The invention relates to mixtures of 1,1,1,3,3-pentafluoropropane and 1,1,1,3,3-pentafluorobutane. More particularly the invention relates to blowing agent compositions containing 1,1,1,3,3-pentafluoropropane and 1,1,1,3,3-pentafluorobutane.
The class of foams known as low density rigid polyurethane or polyisocyanurate foam has utility in a wide variety of insulation applications including roofing systems, building panels, refrigerators and freezers. A critical factor in the large-scale commercial acceptance of rigid polyurethane foams in the building insulation industry has been their ability to provide a good balance of properties. Rigid polyurethane and polyisocyanurate foams are known to provide outstanding thermal insulation, excellent fire properties and superior structural properties at reasonably low densities.
The methods of producing polyurethane and polyisocyanurate foams are generally known and consist in general of the reaction of an organic polyisocyanurate (including diisocyanate) and a polyol or mixture of polyols in the presence of a volatile blowing agent, which is caused to vaporize by the heat liberated during the reaction of isocyanate and polyol. This reaction can be enhanced through the use of amine and/or other catalysts as well as surfactants. The catalysts ensure adequate curing of the foam, while the surfactants regulate and control cell size. Flame-retardants are traditionally added to rigid polyurethane or polyisocyanurate foam to reduce its flammability.
The foam industry has historically used liquid fluorocarbon blowing agents such as trichlorofluoromethane (CFC-11) and 1,1-dichloro-1-fluoroethane (HCFC-141b) because of their ease of use in processing conditions. Fluorocarbons act not only as blowing agents by virtue of their volatility, but also are encapsulated or entrained in the closed cell structure of the rigid foam and are the major contributor to the low thermal conductivity properties of rigid urethane foams.
The use of a fluorocarbon as the preferred commercial expansion or blowing agent in insulating foam applications is based in part on the resulting k-factor associated with the foam produced. K-factor is defined as the rate of transfer of heat energy by conduction through one square foot of one inch thick homogenous material in one hour where there is a difference of one degree Fahrenheit perpendicularly across the two surfaces of the material. Since the utility of closed-cell polyurethane-type foams is based, in part, upon their thermal insulation properties, it would be advantageous to identify materials that produce lower k-factor foams.
1,1,1,3,3-pentafluoropropane (HFC-245fa) and 1,1,1,3,3-pentafluorobutane (HFC-365mfc) are known blowing agents. See U.S. Pat. Nos. 5,496,866; 5,574,192; 5,917,098; and 6,080,799, herein incorporated by reference in their entirety.
It has now been discovered that foams prepared with a blowing agent comprising a blend of HFC-245fa and HFC-365mfc, wherein HFC-245 is present in a major amount, exhibit improved k-factor over both HFC-365mfc and HFC-245fa alone. The improvement is non-linear, which is unexpected since the mixture is non-azeotropic.
The invention provides mixtures comprising, consisting essentially of or consisting of 1,1,1,3,3-pentafluoropropane (HFC-245fa) and 1,1,1,3,3-pentafluorobutane (HFC-365mfc). Preferably, the compositions comprise from about 51 to about 99 weight percent 1,1,1,3,3-pentafluoropropane and from about 1 to about 49 weight percent 1,1,1,3,3-pentafluorobutane. More preferably, the compositions comprise from about 75 to about 99 weight percent 1,1,1,3,3-pentafluoropropane and from about 1 to about 25 weight percent 1,1,1,3,3-pentafluorobutane.
In one embodiment, the invention provides a blowing agent comprising the composition of the invention.
In another embodiment, the invention provides a method of preparing foam compositions based on isocyanate which comprises reacting and foaming a mixture of ingredients which will react to form polyurethane or polyisocyanurate foams in the presence of the blowing agent composition of the invention.
In yet another embodiment, the invention provides a closed cell foam prepared from a polymer foam formulation containing the blowing agent composition of the invention.
In yet another embodiment, the invention provides a polyol premix composition comprising a polyol and the blowing agent composition of the invention.